Mastering the Art of String Formatting in C#

The Basics of String.Format()

The String.Format() method is a powerful tool that allows you to create formatted strings with ease, making your code more readable and efficient. It takes two parameters: a format string and an object to format.

The format string contains placeholders, known as format items, which are replaced by the object’s values. The syntax is simple:

String.Format(format, args)

Example 1: A Simple Format String

Consider the following example:

string output = String.Format("There are {0} apples.", 5);
Console.WriteLine(output); // Output: "There are 5 apples."

In this example, {0} is the format item, and the variable number is inserted in its place.

Working with Multiple Format Items

If you need to format multiple values, you can use multiple format items:

string name = "John";
string food = "pizza";
string output = String.Format("My name is {0} and I love {1}.", name, food);
Console.WriteLine(output); // Output: "My name is John and I love pizza."

In this case, {0} is replaced by the name variable, and {1} is replaced by the food variable.

Controlling Spacing and Alignment

You can specify the width of the string and even align it left or right:

string programiz = "Programiz";
string rightAligned = programiz.PadRight(20);
string leftAligned = programiz.PadLeft(20);
Console.WriteLine(rightAligned); // Output: "Programiz          "
Console.WriteLine(leftAligned);  // Output: "         Programiz"

Formatting Dates and Numbers

String.Format() isn’t just limited to strings. You can also use it to format dates and numbers.

For dates, use format specifiers like {0:D} for a long date format:

DateTime date = DateTime.Now;
string output = String.Format("Today's date is {0:D}", date);
Console.WriteLine(output); // Output: "Today's date is Friday, June 12, 2020"

For numbers, use {0:D} for decimal, {0:X} for hexadecimal, and more:

int number = 123;
string decimalOutput = String.Format("The decimal value is {0:D}", number);
string hexOutput = String.Format("The hexadecimal value is {0:X}", number);
Console.WriteLine(decimalOutput); // Output: "The decimal value is 123"
Console.WriteLine(hexOutput);    // Output: "The hexadecimal value is 7B"

Common Format Specifiers

Here are some common format specifiers for dates and numbers:

• Date format specifiers:
  • D: long date
  • d: short date
  • t: long time
  • T: short time
• Number format specifiers:
  • D: decimal
  • X: hexadecimal
  • C: currency
  • E: exponential